where Te and Ti denote the Gammas of the earlier and later options respectively.
The relative weights of the earlier and later options can be chosen so
that T-p = 0. Once the portfolio is made Gamma neutral, the underlying
security can be added to the portfolio in such a way as to make the portfolio
Delta neutral. The reader should keep in mind that the underlying
security will have a V = 0 and thus Gamma neutrality for the portfolio
will be maintained while Delta neutrality is achieved. Thus Eq. (9.2) for a
Gamma neutral portfolio reduces to